Bio 2

Origins of Life

  • Origin of life is hypothesized to be 4.2 billion years old, the oldest rocks are only 3.85 billion years old.

  • The early earth in Hadean was a hot molten ball that was completely inhospitable  at the time of formation 4.6 billion years ago.

  • The ancient earth had an atmosphere different from the modern atmosphere.

  • What conditions could life survive in?

    • Not many organisms alive on the modern earth could survive

    • The earliest would have been unicellular organisms or simpler and would have been anaerobic (didn’t require oxygen) 

  • The first membrane bound organisms began as enclosed collections of nucleic acids and proteins that became encased in a bubble of phospholipids.


2/26/2025

  • Microbe refers broadly to any kind of microscopic (single celled organisms), including such as bacteria and algae.

  • Prokaryote is a single celled organism that lacks a nucleus and membrane bound organelles.

    • Has DNA, makes it a cell.

    • Ribosome- synthesize proteins.

    • Plasma membrane and cell wall.

    • Has Pili (hair that sticks to things)

    • Flagella- (tails made of protein to help the bacteria swim.

  • Eukaryotic cell is a cell characterized by the presence of a nucleus, and they often contain other membrane bound organelles.

    • Arose 1.9 to 1.4 billion years ago.

  • According to endosymbiosis theory, the origin of mitochondria and chloroplasts is that aerobic bacteria and photosynthetic bacteria took up residence in ancient host cells, possibly after failed consumption.

  • Metabolism

    • Heterotroph- acquire carbon by consuming other organisms

    • Autotroph- acquire carbon from inorganic sources, like CO2

    • Phototrophs- acquires energy from from light

    • Chemotroph- acquire energy from chemicals. 

  • Chemotrophs

    • Aerobes use O2 to produce ATP, and obligate aerobes die without oxygen.

    • Anaerobes- do not require oxygen, and may either occur as obligate anaerobes that are killed by oxygen.

      • The presence of oxygen is therefore a controlling factor for what types of bacteria can exist.

  • Bacteria and archaeans outwardly appear similar , but distinguished based on their DNA sequences and chemical composition.

3/3/2025

  • Protists- Classifying them is difficult because they are not a single clade.

    • First defined as a eukaryote that are not plants, fungi, or animals. 

    • DNA evidence has allowed for protists to be reclassified into dozens of groups.

  • Classifying Protists.

    • Algae- resemble plant cells.

    • Slime molds and water molds- resemble fungal cells.

    • Protozoa- resemble animal cells.

  • Fungi- The eukaryotic organisms closely related to animals.

    • Includes mushrooms

    • Most are multicellular, some are unicellular (yeast)

    • Chemical and metabolic features 

      • Store excess energy in glycogen, use the modified carbohydrate chitin

    • Essential decomposers, nature's garbage processors.

  • They are heterotrophic decomposers with external digestion.

  • Made of thin filaments called hyphae that produce a mycelium that secrete.

  • Haploid- half the normal number of chromosomes.

  • Diploid- normal amount of chromosomes

  • Fungi can create symbiotic interactions with plants and cyanobacteria.

  • They may occur as endophytes inside plant tissues creating substances that defend plants from herbivores.

  • Join with plant roots to form mycorrhizae- the fungi helps the plant get water and minerals through the roots.

  • Lichen- can break down inorganic compounds.

3/5/2025

  • Plants- multicellular eukaryotic organisms classified into the Kingdom Plantae

  • Modern plants can be divided into 4 groups

    • Bryophytes

      • Bryophytes- seedless plants without vascular tissue.

    • Seedless Vascular plants

      • Have xylem and phloem

      • Have an underground stem called the rhizome.

    • Gymnosperms

    • Angiosperms

  • Plants are photoautotrophs that use photosynthesis to obtain energy and carbon.

  • Plants have above ground stalks called stems that support leaves, which are the sites of photosynthesis.

  • Leaves have stomata that allow gases to leave and enter.

    • Coated in a waxy cuticle that prevents loss of water and gas.

  • Some plants are vascular (internal tubes)

    • Xylem transport water and minerals from the roots to the stem and leaves

    • Phloem transports sugars away from the leaves to the roots and non-green plant portions.

    • Xylem contains lignin, a strong polymer that allows support throughout the plant.


3/17/2025

  • Seed plants- use a modified sporophyte called a seed to reproduce.

    • 2 Major groups

      • Gymnosperms

      • Angiosperms

  • Specialized plants include the seed plants that use pollen to allow for the fertilization across far distances and seeds to spread offspring far from the site of fertilization.

  • Seeds are reproductive structures with three main components.

    • Outer seed coat protects the seeds

    • Intermediate endosperm made of starch and oil to nourish the young plant.

    • Inner embryo (made from the fusion of egg and sperm).

  •  Gymnosperms (Gymno=naked, Sperm= seed) not enclosed by fruit

    • Include pine trees, shrubs, leaves may be needles, blades, and broad fans.

    • Cycads

    • Ginkgos

    • Conifers- pine trees

  • Angiosperms (angio = vessel, sperm= seed)- flowering plants that enclose their seeds in fruit

    • Fruit- bribe to animals to take seeds far from the parent plant.

    • Double Fertilization

 3/19/2025

  • Animals are a kingdom of eukaryotes.

  • Some animals can survive in the vacuum of space.

  • Animal life began in water.

    • 570 MYA

    • The earliest animal forms are known from marine rocks of the Precambrian eon– the Ediacaran animals died out 544 MYA and left no known modern descendants.

    • Many still living things originated in the ocean.

      • Sponges, jellyfish, mollusks, etc…

  • Animals are multicellular eukaryotes that lack cell walls.

  • They are heterotrophic, eating food by ingesting it.

  • Animals have a specialized body plan enabled by the following

    • They have symmetry

    • Specialized tissues

    • Special stages of development.

  • Animals are classified by their pattern of body symmetry.

  • Animals with bilateral symmetry have one plane of symmetry.

  • Animals with radial symmetry have multiple planes of symmetry.

  • In early development animals undergo a process called gastrulation.

  • 3 layers 

    • Ectoderm

    • Mesoderm

    • Endoderm

  • Endoderm develops into the digestive tract.

  • Animals have an incomplete digestive tract if the mouth both takes in food and ejects wastes.

  • Animals have a complete digestive tract if food passes in one direction and goes out another hole.

  • Protostomes are the animals that develop their mouth first (worms, mollusks, and arthropods)

  • Deuterostomes are the animals that develop their anus first.

  • Cnidarians are simple animals that have stinging cells

    • Two layered

    • Incomplete digestive tract.

  • More than 5 pairs of legs meriopod.


3/24/2025


  • Deuterostomes are animals that develop the anus first and the mouth second when forming their digestive system.

    • Two Major groups

      • Echinoderms- are animals named for their ‘spiny skin’- radially symmetric.

        • Water vascular system- accommodates the circulatory, respiratory, and excretion systems.

      • Chordates- a diverse group of animals and have some of the greatest diversity in appearance of any phylum

        • Most primitive chordates occur as invertebrate organisms. Advanced chordates include the familiar vertebrates, like humans.

        • Features

          • Notochord- a flexible rod that provides structure and support (made from cartilage) 

          • Dorsal, hollow nerve cord- A nervous system structure that runs parallel to the notochord.

          • Pharyngeal slits or pouches- used for filter feeding.

          • Postanal tail- contains powerful muscles that aid in swimming or other movement.

  • Tunicates- simple sessile, marine organisms

  • Lancelets- resemble simple fish but use their tail to anchor to shallow sea sediments and filter feed.

  • Craniates- major group of chordates

  • Vertebrates are descended from a craniate ancestor.

  • Amphibians- named for their ability to lead a double life on both dry and in watery habitats.

  • Reptiles

    • Amniotic egg envelopes a developing embryo to prevent drying out and to exchange gases with the environment.  


3/26/2025

  • Mammals are animals that produce milk for nourishment of their offspring.

    • Endothermic

    • Most mammals are covered in hair and have specialized teeth.

  • Mammals are classified into:

    • The monotremes are named for having a single opening for both the digestive and reproductive tract, which is used for laying eggs.

    • The marsupials, which give birth to live (but immature) offspring that are nourished and complete their development in a pouch.

    • The placentals, which give birth after a comparatively long gestation period with the aid of a placenta, a temporary reproductive organ that produce hormones and connect the fetal and maternal circulatory systems.

  • Humans are a type of primates.

    • Features include: flat nails, grasping hands and opposable thumbs, and eyes in the front of your head creating depth perception.

  • The family of primates also includes prosimians (lemurs, tarsiers, lorises, aye-ayes, and galagos), monkeys, and apes

  • Humans descended from other ape ancestors – human evolution occurred. 😒

  • Evolution of the brain